The present invention relates to a developing method and an image forming method, and more particularly to a developing method and an image forming method performed to form an image in an electrostatic latent image developing mode employed in a printer, a copying machine, etc.
A quantity of charge of toner used to form an image in an electrostatic latent image developing mode is known to have significant influences on image formation. More concretely, in the electrophotographic process, toner adheres to a photosensitive body due to the charging characteristic of individual toner particles, and is then transferred onto a transfer body, whereby an image is formed. Hence, it is thought that most of the problems, such as fogging, scattering, transfer dust, deterioration over time, and environmental deterioration, which need to be addressed in the electrophotographic process, are attributed to wrong toner incapable of controlling a quantity of charge. A crucial problem in the related process is therefore to charge the toner as homogeneously as possible.
In regard to an image forming method performed by controlling the charging characteristic of toner, a cleaner-less image forming method has been proposed as described in JP-A-5-2287, page 3, in which the intrinsic electric resistance value, R, of developing toner to be used satisfies R≧1×1013 Ω·cm, and a quantity of charge, qt, of the developing toner is set to 0.5[mC/kg]≦|qt|≦40[mC/kg]. This image forming method, however, merely defines a quantity of charge of the developing toner in relation with the intrinsic electric resistance value, and fails to suggest a relation between a charge quantity distribution and a particle size distribution of toner as an aggregation of individual particles.
Also, second example of a developing method has been proposed (see JP-A-8-129268, pages 2 to 3), in which, given Y as an index indicating voltage dependency of a developer, containing magnetic carriers and toner, found from a resistance value, R500 [Ω·cm], at a field intensity of 500 V/cm and a resistance value, R2500 [Ω·cm], at a field intensity of 2500 V/cm, and X as a particle count ratio [%] indicating a percentage of non-changed toner of the total toner in a range, Q/D<0.2, within a charge quantity distribution of the toner defined by a quantity of charge, Q [femt.C], and a particle size, D [μm], of the toner, then an electrophotographic image developer set to satisfy Y>(3X/400)+1 is used. This method, however, uses two-component toner containing magnetic carriers and toner; moreover, it merely defines a particle count ratio of non-charged toner, which causes smearing of an image, in relation with resistance values at certain field intensities, and no consideration is given to a relation between a charge quantity distribution and a particle size distribution of toner as an aggregation of individual particles.
Currently, a quantity of charge of toner is understood as a mere total quantity of charge in toner with reference to a mass of the toner, and it is therefore impossible to control a quantity of charge of individual toner particles. As a result, the presence of wrong toner incapable of controlling a quantity of charge is allowed, which not only gives rise to fogging or the like, but also deteriorates transfer efficiency and thereby impairs an image quality. Deterioration of transfer efficiency not only increases waste toner remaining on the photosensitive body after the completion of transfer, but also prevents omission or simplification of a cleaner mechanism used to clean the waste toner (adaptation of a cleaner-less process). As described, the developing methods proposed to date have a limit in the improvement of an image quality in image formation, a reduction of an apparatus in size, etc.